[REBOL] Re: Bug in Area
From: nitsch-lists:netcologne at: 3-Nov-2001 3:46
RE: [REBOL] Re: Bug in Area
Hi Brett
[brett--codeconscious--com] wrote:
> Hi Volker,
>
> > i think face/line-list is a cache.
>
> Yes I think that is most likely, and for the reasons you give.
>
> > face/dirty? is set if you change the text.
>
> Remember, the Rebol/View Develop Guide says of VID:
> RVDG> VID is implemented as a layer that rides on top of the REBOL/View
> graphical compositing system.
>
> I could be wrong but I think the dirty? flag is part of the VID layer not
> the lower level View faces. I figure that if I'm using the VID layer and I
> do something it doesn't know about, then I should work to ensure that VID is
> in a consitent state when I'm finished. For ordinary uses of VID there is no
> issue.
>
> > if face/dirty?[confirm "really exiting without saving?"]
> > inbuild editor uses that for example.
>
> Mostly true, but I've documented a minor case where it fails. This happens
> to be a case where the VID layer doesn't pick up a situation that sometimes
> can be classed as being a dirty state. [Gee this language is bizarre :) ]
>
> > opposition! ;-)
> > view has your update in a way, but not that obvious.
>
> Maybe you misunderstand me :)
> My "update" suggestion refers to keeping the state variables consistent -
> not changing the lean behaviour of the compositing engine or anything more.
i hope i had understand you ;-)
if i want to change a face, i call its update with appropriate parameters.
in other systems, this parameters are given the usual way: update x y z .
in rebol we set parameters in the face. then call show.
so state-variables are the parameters.
> Gregg, Paul and Ammon I think have shown that it is fairly easy to cause an
> area to go a bit haywire. Remember Gregg said:
>
> GI> I think there is a bug in there (i.e. we shouldn't
> GI> have to manually clear the line-list when we update the text).
>
it may be automatic in some releases.
Not by a function, but because of 'query .
that would allow 'redraw to check if the text has changed.
unfortunally only one function should clear this flag,
but show/redraw would be a good place for it?
today, for fields (one line, <200chars) i can avoid it
and for areas i do it allways. simple rule.
maybe the name could be more obvious,
face/text-analysed: none or that?
> I must admit I thought that the line-list was part of the VID layer. Now I'm
> not so sure. I have to agree with Gregg that manually clearning the
> line-list seems odd. Though I think for performance the programmer should
> have some way to tell the engine to recalculate the cache when he/she has
> finished manipulating the text. For example you might be inserting text all
> over the place in a large body of text - calculating on each modification
> may be expensive. Calling a function rather than clearing the field seemed
> more natural to me.
me to first. after a while i got the view-way:
tell all you want and then call a function to process
that (like show).
> <snip redraw description>
>
> > in rebol one can change various properties
> > and action starts in the last possible moment, only one.
> > more efficient and easier to track,
> > but sometimes more code.
> > i like it more :-)
>
> I like the View compositing engine and VID too, though some tweaking might
> be useful to make them more programmer friendly. :-)
>
> Brett.
>
-Volker
